Epidemiological studies have consistently reported the correlation of colon cancer incidence with diet. In particular, the positive correlation of high dietary fat with colorectal cancer is well documented and the mode of action is, at least, partly understood. However, any consistent negative correlation of dietary fiber with colon cancer incidences remains to be identified. Increases in dietary fiber are known to alter several physiological parameters by binding water, decreasing transit time, increasing fecal volume, binding bile acids and altering the intestinal microflora. Whether these changes exert a truly protective effect against colon cancer or the correlation simply reflects changes in fecal volume has yet to be determined. Therefore, this study was designed to investigate the effect of specific well-characterized brans (soybean, corn, hard spring wheat, and soft winter wheat) on the tumor incidence in mice treated with 1,2-dimethylhydrazine (DMH). Beginning at 11 weeks of age, we inject barrier-derived male BALB/c mice subcutaneously weekly for 10 weeks with DMH (20 mg/kg body weight); this model was chosen because of the specificity for the production of distal colon and rectal tumors without tumors arising in other tissues. The low fat diets containing 20% bran are highly controlled being commercially synthesized to our specifications. Diets are given to mice beginning at 8 weeks of age and continuing throughout the experimental period until sacrifice. At time of sacrifice (10 months after first DMH injection), mice will be killed; colons will be inflated with Telly's fixative, cleared and stained. Tumors will be identified through a dissecting scope, sectioned and stained and examined histologically. Groups will be compared and diets will be evaluated regarding their effects on tumor incidences, malignancy, and tumors per tumor-bearing mouse.